Optimization of Multicycle THz generation using versatile optical pulse trains

Low efficiencies for narrowband optical-to-terahertz down-conversion remain a primary limiting factor for many applications of intense, laser-driven terahertz (THz) sources, highly sought after in material science and THz acceleration. Although simulations predict improvements in efficiency by using tailored trains of laser pulses as a driver, few studies have targeted this configuration. Here, we report on an experimental campaign using a flexible pulse-train driver to study THz generation in periodically-poled lithium niobate focusing on the effects of pulse train number, as well as crystal length and temperature. We also investigate the role of parasitic second harmonic generation.